Shielding for emi-sensitive electronic components and or circuits of electronic devices

ABSTRACT

A shielding apparatus for EMI-sensitive electronic components, especially for radio transmitting devices and/or radio receiving devices of telecommunication terminals for contactless telecommunication, such as cordless telephones and mobile telephones and similar, which can be constructed without using expensive manufacturing and assembly steps without any extra space requirement. The EMI-sensitive electronic components and/or circuits are arranged on a separate, at least double-layered printed circuit board and are embodied as a printed circuit board module. Said circuit board and another separate, at least two-layered circuit board which includes a recess for the EMI-sensitive electronic components and/or circuits and which is embodied in the form of a base printed circuit board, are joined together by soldering, preferably in the region of contact areas, to form a unit such that a cage is formed by the recess which is disposed between two metal surfaces being respectively connected to the shielding surfaces by means of continuous, highly adjacent contacts. The cage shields the EMI-sensitive electronic components and/or circuits on all sides.

FIELD OF TECHNOLOGY

The present invention relates to shielding for EMI-sensitive electroniccomponents and/or circuits of electronic devices, in particular forradio transmitting devices and/or radio receiving devices oftelecommunication terminal devices for wireless telecommunication, suchas cordless telephones, mobile telephones and the like.

BACKGROUND

Electronic devices predominately have a single printed circuit boardfrom which device functions are performed. In the case of devices havingmore than two printed circuit boards, modular technology is used withregard to the structure of the printed circuit board. Modular technologyis preferably used in cases when the circuits and/or components in theelectronic device place different requirements on the printed circuitboard. The term “circuits” encompasses circuit components, circuitelements such as conductive track structures, etc., and/or circuitwiring between the circuit components, or between the circuit componentsor circuit elements and the structural elements.

As an example, in a high-frequency (HF) device including electronic HFcircuits and HF components as well as low frequency (LF) circuits and LFcomponents, the LF circuits and components may, for economic reasons, beintegrated on a printed circuit board which, unlike the printed circuitboard for the HF circuits and components, needs to meet lowerrequirements with respect to circuit board quality because of the lesscritical physical characteristics of the LF circuits and components.Accordingly, the printed circuit board with the HF circuits andcomponents will typically appear as a multilayer (e.g., FR4) printedcircuit board, whereas the printed circuit board with the LF circuitsand components will typically appear as a different multilayer printedcircuit board (e.g., FR2, FR3).

To minimize the electromagnetic radiation into and from the HF circuitsand components on the FR4 printed circuit board module, in addition tothe improved printed circuit board material for the HF module, ashielding element is used that shields the EMI-sensitive electroniccomponents and/or circuits themselves or the entire FR4 printed circuitboard module.

To shield electronic components and/or circuits susceptible toElectro-Magnetic Interference (EMI)—such as high-frequency (HF)components and/or high-frequency (HF) circuits used in radiotransmitting/receiving devices metal and/or ceramic shielding elements,which shield the EMI-endangered electronic components and/or circuitsthemselves or the entire printed circuit board, are additionally placedon the printed circuit board of the EMI-sensitive electronic componentsand/or circuits; to shield the EMI-sensitive electronic componentsand/or circuits themselves, or the entire printed circuit board.

Examples, of shielding housings or shielding devices are disclosed inU.S. Pat. No. 5,895,884, EP 0 886 464 A2, EP 0 735 811 A2 and DE 199 45427 C1, and are incorporated by reference in their entirety herein.

In the case of cordless telephones it is known, for example, to provideor configure the housing as a whole, or the frame or lid of the housing,with shielding elements, or to cover the HF components and/or HFcircuits with cup- or pot-shaped metal shielding elements.

It is also known in the prior art to shield HF components and/or HFcircuits with resistance pastes and so-called Gore foils, the Gore foilsgenerally being used to shield capacitors.

With the known shieldings for high-frequency electrical componentsand/or circuits, the use of additional shielding elements isdisadvantageous because, firstly, additional manufacturing and assemblysteps are required and, secondly, the space requirement of thehigh-frequency electrical components and/or circuits is increased byshielding configured in this way.

Accordingly, there is a need to provide shielding for EMI-sensitiveelectronic components and/or circuits of electronic devices, inparticular for radio transmitting devices and/or radio receiving devicesof telecommunication terminal devices for wireless telecommunication,such as cordless and mobile telephones and the like, that can bemanufactured without complex and expensive manufacturing and assemblyoperations and without an additional space requirement.

BRIEF SUMMARY

One exemplary embodiment disclosed herein arranges EMI-sensitiveelectronic components and/or circuits of electronic devices on aseparate, preferably double-layered, printed circuit board that ispreferably in the form of a printed circuit board module. This printedcircuit board also includes a further separate, at least double-layeredprinted circuit board, preferably in the form of a base printed circuitboard carrying non-EMI-sensitive electronic components and/or circuits.A recess is also provided for the EMI-sensitive electronic componentsand/or circuits, where they are preferably joined together by solderingand preferably in the region of contact areas, to form a unit, such thata cage is formed by the recess arranged between two metal layers(printed circuit board layers) that are configured as earth faces, eachearth face being connected to the contact areas via very closely spacedinterfacial connections, with the cage shielding the EMI-sensitiveelectronic components and/or circuits on all sides.

The contact area may either be formed by the interfacial connectionsleading to it, or it may additionally have a shielding face that isconnected to the interfacial connections leading to the contact area.

In the printed circuit board module, the earth face, which almostcompletely covers the printed circuit board module, is preferablylocated on the side facing away from the EMI-sensitive components and/orcircuits, and the contact area, which encompasses the components and/orcircuits, is preferably located on the components side and/or circuitsside. On the base printed circuit board, the contact area, whichencompasses the recess, is preferably located on the printed circuitboard side having the recess opening and the earth face, the area ofwhich extends beyond the base surface of the recess or is identical withit, is preferably located on the side of the printed circuit boardfacing away from the recess opening.

When the two printed circuit boards are joined together, preferably inthe region of the contact areas (if the two printed circuit boards arelocated one above the other), the EMI-sensitive electronic componentsand/or circuits disappear in the recess. In the assembled state, theshielding cage is formed by very closely spaced interfacial connections,which are separated preferably by a distance of less than one-tenth ofthe wavelength λ of an electromagnetic radiation emitted by electroniccomponents/circuits, which interfacial connections connect the earthface for each printed circuit board with the respective contact area.

This arrangement has the advantage that the printed circuit board moduleto be shielded does not require any further external shielding device,so that additional material costs are not incurred because comparableshielding is achieved by the cage formed by the two printed circuitboards with the recess, the interfacial connections, the earth faces andthe contact areas. Furthermore, any repair that may be needed is nowpossible on the printed circuit board module because no shielding ispresent at this stage of manufacturing. This facilitates the inspectionof solder points on the module in the context of quality assurance andfault tracing. The overall height of the printed circuit board module isalso reduced since no additional shielding device is required on theprinted circuit board module.

Because the existing base printed circuit board is also used asshielding for a printed circuit board module with EMI-sensitiveelectronic components and/or circuits, the use of an additionalshielding device is dispensed with. In this case it is less materialwhether the printed circuit board module is fitted to the base printedcircuit board, or whether the base printed circuit board is fitted tothe printed circuit board module. This means that if, in the first case,the adhesion force of some components and/or circuits is insufficient onrepeated soldering, so that they become detached from the solder pad,then the base printed circuit board is fitted to the printed circuitboard module.

Shielding for EMI-sensitive electronic components and/or circuits isespecially advantageous in such telecommunication terminal devices forwireless telecommunication in which an HF module, e.g. a radiotransmitting and/or radio receiving device, or other circuit parts withhigh clock frequencies, e.g. a microprocessor, are used.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details, features and advantages of the invention are elucidatedin more detail below with reference to the exemplary embodimentillustrated in FIGS. 1 to 4, in which:

FIG. 1 is a view from the components side and/or circuits side of afirst printed circuit board designed for non-EMI-sensitive electroniccomponents and/or circuits in the form of a base printed circuit board;

FIG. 2 is a view from the components side and/or circuits side of asecond printed circuit board designed for EMI-sensitive electroniccomponents and/or circuits in the form of a printed circuit boardmodule;

FIG. 3 is a view of the side of the printed circuit board facing awayfrom the components side and/or circuits side of the second printedcircuit board designed for EMI-sensitive electronic components and/orcircuits in the form of a printed circuit board module; and

FIG. 4 shows sectional representations of the first printed circuitboard according to FIG. 1 along the section line A-A′, viewed in thedirection of the arrows, and of the second printed circuit boardaccording to FIGS. 2 and 3 along the section line B-B′, viewed in thedirection of the arrows in each case.

DETAILED DESCRIPTION

FIG. 1 shows a top view of a preferably double-layered first printedcircuit board 1 in the form of a base printed circuit board which on oneside comprising a first printed circuit board layer has anon-HF-component 10, preferably in the form of a surface mounting deviceand representative of a multiplicity of non-EMI-sensitive electroniccomponents and/or circuits, and on an opposed side comprising a secondprinted circuit board layer has a first earth face 13, preferablyextending over the entire area of the printed circuit board 1. However,as explained below, other embodiments are possible as well. Because theearth face 13 cannot be seen in FIG. 1 as a result of the top viewrepresentation of the printed circuit board 1, it is represented bybroken lines in FIG. 1. The earth face 13 may be configured either as acontinuous surface or as a grid surface with a grid line spacing of lessthan one-tenth of the wavelength λ of an electromagnetic radiationemitted by electronic components/circuits.

Alternatively, it is also possible, although not explicitly shown inFIG. 1, for the above-mentioned non-HF-component 10, or other componentsand/or circuits, to be arranged on the second printed circuit boardlayer with the earth face 13, although separated from the latter. It isalso possible for the printed circuit board 1 to have more than twolayers.

An opening 110 of a recess 11, let into the printed circuit board 1, 15located on the components side and/or circuits side of the first layerof the printed circuit board 1, in addition to the non-HF-component 10.Recess 11 has a base surface 111 located between the first layer on thecomponents side and/or circuits side of the printed circuit board 1, andthe second layer on the side of the printed circuit board facing awayfrom the components side and/or circuits side.

The surface areas of the base surface 111 and of the earth face 13 arepreferably configured so that the earth face 13 in the second printedcircuit layer corresponds at least to the area of the base surface 111of the recess 11. It is also possible that the earth face 13, instead ofbeing arranged in the second printed circuit board layer, is locatedbetween the second layer and the base surface 111 or even in the planeof the base surface 111 itself, provided it is ensured in each case thatno circuit lines or conductive tracks are disposed between the basesurface 111 and the earth face 13. Attention must be paid to thisespecially in the case of printed circuit boards having more than twolayers.

In the first layer of the printed circuit board 1, the opening 110 ofthe recess 11 has, for shielding purposes, a metal edge configured as afirst shielding face 12 that will be explained in more detail below inthe description of FIG. 4. Provided in the edge of the opening or in theshielding face 12 are first gaps 120 for external lines 4 (cf. FIG. 2)that are preferably constructed so that external lines 4 can beconnected to signal lines 5 located outside the shielding face 12 in thefirst layer of the printed circuit board 1 without touching theshielding face 12 (i.e., without having contact with the shielding face12).

The metal edge of the opening or the shielding face 12 is alsoelectrically connected to a multiplicity of preferably resin-filledfirst interfacial connections 14 which, except for the zone of the gaps120, are arranged on the printed circuit board 1 beyond (outside) theentire shielding face 12. The distance between two neighboringinterfacial connections 14 on the printed circuit board 1 is less thanλ/10, where λ is the wavelength of the electromagnetic radiation emittedby electronic components/circuits.

In the printed circuit board 1 illustrated in FIG. 1, the interfacialconnections 14 extend from the first printed circuit board layer to thesecond printed circuit board layer and connect the shielding face 12 inthe first layer to the earth face 13 in the second layer. It is notedthat if the earth face 13 is not located in the second printed circuitboard layer but in a different layer which, for example, is not anexternal layer, the interfacial connections 14 extend preferably only asfar as this other layer.

Alternatively to the structure of the printed circuit board 1 describedand illustrated, in which the shielding face 12 and the interfacialconnections 14 form a first contact area 12, 14, it is also possible todispense with the shielding face 12. In this case the contact area 12,14 is formed by the interfacial connections 14 which lead with one endinto the contact area while their other ends are connected to the earthface 13.

FIG. 2 illustrates a top view of the preferably double-layered printedcircuit board 2 in the form of a printed circuit board module that hason one side comprising a first layer an HF component 20, preferablyagain in the form of a surface mounting device and representative of amultiplicity of EMI-sensitive electronic components and/or circuits. Onan opposing side of the board is a second layer having a second earthface 21. Since the earth face 21 cannot be seen in FIG. 2 as a result ofthe top view representation of the printed circuit board 2, the earthface 21 and its extension on the printed circuit board 2 is shownseparately in FIG. 3. The earth face 21 may again preferably beconfigured either as a continuous surface or as a grid surface with agrid line spacing of less than one-tenth of the wavelength λ of anelectromagnetic radiation emitted by electronic components/circuits.

Again, it is further possible for the printed circuit board 2, like theprinted circuit board 1, to have more than two layers.

Located in the first layer of the printed circuit board 2 on thecomponents side and/or circuits side, in addition to the HF-component20, is a second shielding face 22 which again serves the purpose ofshielding to be explained in more detail in the description of FIG. 4shielding face 22 corresponds substantially, with respect to shape,dimensions, extent and material, to the first shielding face 12 shown inFIG. 1.

Accordingly, shielding face 22, like shielding face 12, has in the sameplace second gaps 220 that correspond substantially to the first gaps120.

In the shielding face 22 the gaps 220 are provided for signal lines 4which correspond to the external lines mentioned in the description ofFIG. 1 and which do not touch the shielding face 22 (i.e., have nocontact with the shielding face 22).

In addition, the shielding face 22 is preferably electricallyconnected—like the first shielding face 12 with the first interfacialconnections 14 in FIG. 1—to a multiplicity of preferably likewiseresin-filled, second interfacial connections 23 that, with the exceptionof the zone of the gaps 220, are arranged on the printed circuit board 2in the zone of the entire shielding face 22, unlike the situation inFIG. 1, i.e. not beyond (outside) the entire shielding face 12 on theprinted circuit board 1.

Alternatively, however, it is also possible for the interfacialconnections 23 to be arranged, like the interfacial connections 14,beyond (outside) the entire shielding face 22 on the printed circuitboard 2. Conversely, however, it is also possible for the interfacialconnections 14 in FIG. 1, like the interfacial connections 23 in FIG. 2,to be arranged in the zone of the entire shielding face 12 on theprinted circuit board 1.

The distance between two neighboring interfacial connections 23 on theprinted circuit board 2 is again less than λ/10, λ being the wavelengthof the electromagnetic radiation emitted by electroniccomponents/circuits.

In the printed circuit board 2 shown in FIG. 2 the interfacialconnections 23 extend from the first printed circuit board layer to thesecond printed circuit board layer and connect the shielding face 22 inthe first layer to the earth face 21 in the second layer. It is notedthat if the earth face 21 is not located in the second printed circuitboard layer, but perhaps in a different layer (e.g., is not an externallayer), the interfacial connections 23 extend preferably only as far asthis other layer.

Alternatively to the structure of the printed circuit board 2 describedand illustrated, in which the shielding face 22 and the interfacialconnections 23 form a second contact area 22, 23, it is also possible todispense with the shielding face 22. In this case the contact area 22,23 referred to is formed solely by the interfacial connections 23 whichlead with one end to the contact area 22, 23 while their other ends areconnected to the earth face 13.

FIG. 3, based on FIG. 2, shows a top view of the preferablydouble-layered second printed circuit board 2, configured as a printedcircuit board module, and includes on the side with the second layer thesecond earth face 21 and on the opposed side with the first layer the HFcomponent 20 representing the multiplicity of EMI-sensitive electroniccomponents and/or circuits. Because the HF component 20 and the signallines 4 cannot be seen in FIG. 3 as a result of the top viewrepresentation of the printed circuit board 2, they are represented bybroken lines in FIG. 3.

In FIG. 3 the interfacial connections 23 are not drawn with broken linesbecause they are not hidden by the earth face 21 and therefore arevisible. The reason is that for process reasons the interfacialconnections 23 are only produced by drilling the printed circuit board 2at the end, i.e. after applying the earth face 21 to the second layer ofthe printed circuit board 2.

FIG. 4 illustrates a cross-sectional/exploded view in which the firstprinted circuit board 1 (FIG. 1) is represented in the unconnected state(exploded state) along the section line A-A′, viewed in the direction ofthe arrows, and the second printed circuit board 2 according to FIGS. 2and 3 is represented in the unconnected state (exploded state) along thesection line B-B′, viewed in the direction of the arrows.

The first printed circuit board 1 is preferably configured as the baseprinted circuit board. It can be seen from FIG. 4 how the recess 11,with the base surface 111 and the recess opening 110, is let into theprinted circuit board 1 and how the earth face 13, the first shieldingface 12 encompassing the recess opening 110 and the first interfacialconnections 14 spaced from one another at a distance of less than λ/10,together with the recess 11, form a first part of a shielding cage 3—soto speak, a shielding cage 3 without a lid—in relation to the firstprinted circuit board 1.

With regard to the second printed circuit board 2, preferably configuredas a printed circuit board module, it can be seen how the earth face 21,the second shielding face 22 that is substantially congruent to thefirst shielding face 12 in FIG. 1 and the second interfacial connections23, again spaced from one another by a distance of less than λ/10, forma second part of the shielding cage 3 (i.e., the lid of the shieldingcage 3) and how the HF component 20 disappears in the recess 11 andtherefore in the shielding cage 3 which shields the HF component 20 onall sides, if the second printed circuit board 2 is placed on the firstprinted circuit board 1 in the direction of the broken arrows.

In the state in which the two printed circuit boards 1, 2 are disposedone above or on the other or in contact in the area of the shieldingfaces 12, 22, they are preferably joined together by means of solderballs 6 in the region of said shielding faces 12, 22. Alternatively,however, other joining techniques achieving the same effect (adhesioneffect) as soldering, e.g. bonding, are also possible.

If the shielding faces are not present, as indicated above, the twoprinted circuit boards 1, 2 are joined, in the state specified, in theregion of the interfacial connections 14, 23 a shown in FIG. 4.Alternatively, however, it is also possible to join the two printedcircuit boards 1, 2 in the specified state outside the contact areas 12,14, 22, 23.

With the soldered or bonded joining of the two printed circuit boards 1the signal lines 4, 5 are also joined to one another. Because of thenecessary electrical connection, soldering by means of the solder balls6 is preferably used as the joining means. Should other possible joiningtechniques also be considered here, it is only necessary to take carethat the alternative joining technique ensures an electrical connectionbetween the signal lines.

The above described description and drawings are only to be consideredillustrative of exemplary embodiments, which achieve the features andadvantages of the invention. Modifications and substitutions to specificprocess conditions and structures can be made without departing from thespirit and scope of the invention. Accordingly, the invention is not tobe considered as being limited by the foregoing description anddrawings, but is only limited by the scope of the appended claims.

1-10. (canceled)
 11. A shielding apparatus for EMI-sensitive components,comprising: a first circuit board, having a plurality of layers havinginterfacial connections, said first circuit board including a first basesurface and a recess opening on one layer in which non-EMI-sensitivecomponents are arranged; a first contact area encompassing the recessopening; a first earth face, which corresponds to an area of the basesurface and the recess opening, wherein the non-EMI-sensitive componentsare arranged outside the first contact area or the first earth face; asecond circuit board, having a plurality of layers having interfacialconnections, said second board including a second base surface on onelayer in which EMI-sensitive components are arranged; a second contactarea encompassing the EMI-sensitive components; and a second earth face,corresponding to an area of the second base surface, wherein the firstand second circuit board are coupled via joining means, and wherein saidEMI-sensitive components are arranged within the recess opening of thefirst printed circuit board, and wherein at least some of theinterfacial connections, together with the recess and the first andsecond earth faces, form a cage in which the EMI-sensitive componentsare shielded.
 12. The shielding apparatus of claim 11, wherein the firstearth face is disposed between the recess opening of the first basesurface and a side of the circuit board facing away from the recessopening.
 13. The shielding apparatus of claim 11, wherein the firstearth face is disposed in a plane of the first base surface.
 14. Theshielding apparatus of claim 11, wherein the first earth face isdisposed in a plane of a side of the circuit board facing away from therecess opening.
 15. The shielding apparatus of claim 11, wherein thesecond earth face is disposed between the EMI-sensitive componentcircuit board layer and a side facing away from the EMI-sensitivecomponent circuit board layer.
 16. The shielding apparatus of claim 11,wherein the second earth face is disposed in a plane of a side facingaway from the EMI-sensitive component circuit board layer.
 17. Theshielding apparatus of claim 11, wherein the interfacial connections arespaced apart by a distance less than one-tenth of the wavelength (λ) ofan electromagnetic radiation emitted by the components
 18. The shieldingapparatus of claim 11, wherein the interfacial connections pass throughtheir respective earth faces.
 19. The shielding apparatus of claim 11,wherein the interfacial connections are filled with a filling material.20. The shielding apparatus of claim 19, wherein the filling material isresin-based.
 21. The shielding apparatus of claim 11, wherein theinterfacial connections are connected to each respective earth face andto a respective contact area.
 22. The shielding apparatus of claim 21,further comprising two gaps between the second contact area and arespective interfacial connection having first signal lines, whereinsaid signal lines transmit signals to and from the EMI-sensitivecomponents on the second circuit board.
 23. The shielding apparatus ofclaim 22, further comprising two gaps between the first contact area anda respective interfacial connection having second signal lines, whereinsaid second signal lines are coupled to the first signal lines outsidethe recess opening.
 24. The shielding apparatus of claim 11, wherein theearth faces are configured as continuous faces.
 25. The shieldingapparatus of claim 11, wherein the earth faces are configured as gridfaces, with grid line spacing of less than one-tenth of the wavelength(λ) of an electromagnetic radiation emitted by the components.
 26. Theshielding apparatus of claim 11, wherein the non-EMI-sensitivecomponents are surface mounted devices.
 27. The shielding apparatus ofclaim 11, wherein the first contact area includes a first shielding facethrough which first interfacial connections pass, and a second shieldingface through which second interfacial connections pass.